This Phase I research will evaluate the capabilities of secondary ion mass spectrometry (SIMS) in performing stable isotope ratio analysis and isotope ratio imaging of hard and soft biological tissues. The research program will specifically evaluate SIMS isotope ratio accuracies and image resolutions in the analysis of Ca and Mg distributions in bone and bone-like materials as well as bone culture tissues incubated in culture media containing natural and isotopically enriched Ca and Mg species. The long term objectives of this research are to develop analytical methodologies for the accurate measurement of stable isotope ratios at lateral resolutions approaching 1 micrometer (um). The ability to perform such measurements could find extensive application in a variety of applications in metabolic and nutritional research in which the rate of absorption and resorption of elements such as Ca and Mg in hard biological tissue could be determined at the cellular and sub-cellular levels.